Bacteria are single-celled organisms that are found almost everywhere, exist in large numbers and are capable of dividing and multiplying rapidly. Most bacteria are harmless, but there are three harmful groups; namely: cocci, spirilla, and bacilla. The cocci bacteria are round cells, the spirilla bacteria are coil-shaped cells, and the bacilli bacteria are rod-shaped. The harmful bacteria cause diseases such as tetanus and typhoid.
Viruses can only live and multiply by taking over other cells, i.e. they cannot survive on their own. Viruses cause diseases such as colds, flue, mumps and AIDS.
Fungal spores and tiny organisms called protozoa can cause illness.
Sterilisation is an act or process that destroys or eliminates all form of life, especially micro-organisms. During the process of plasma sterilisation, active agents are produced. These active agents are high intensity ultraviolet photons and free radicals, which are atoms or assemblies of atoms with chemically unpaired electrons. An attractive feature of plasma sterilisation is that it is possible to achieve sterilisation at relatively low temperatures, such as body temperature. Plasma sterilisation also has the benefit that it is safe to the operator and the patient.
Plasma typically contains charged electrons and ions as well as chemically active species, such as ozone, nitrous oxides, and hydroxyl radicals. Hydroxyl radicals are far more effective at oxidizing pollutants in the air than ozone and are several times more germicidal and fungicidal than chlorine, which makes them a very interesting candidate for destroying bacteria or viruses and for performing effective decontamination of objects contained within enclosed spaces, e.g. objects or items associated with a hospital environment.
OH radicals held within a “macromolecule” of water (fog drop) are stable for several seconds and they are 1000 times more effective than conventional disinfectants at comparable concentrations.
A recent article1 considers the use of OH radicals produced by strong ionisation discharges to eliminate microbial contamination. In this study, the sterilisation effect on E. coli and B. subtilis is considered. The bacteria suspension with a concentration of 107 cfu/ml (cfu=colony forming unit) was prepared and a micropipette was used to transfer 10 μl of the bacteria in fluid form onto 12 mm×12 mm sterile stainless steel plates. The bacteria fluid was spread evenly on the plates and allowed to dry for 90 minutes. The plates were then put into a sterile glass dish and OH radicals with a constant concentration were sprayed onto the plates. The outcomes from this experimental study were:
1. OH radicals can be used to cause irreversible damage to cells and ultimately kill them;
2. The threshold potential for eliminating micro-organisms is ten thousandths of the disinfectants used at home or abroad;
3. The biochemical reaction with OH is a free radical reaction and the biochemical reaction time for eliminating micro-organisms is about 1 second, which meets the need for rapid elimination of microbial contamination, and the lethal time is about one thousandth of that for current domestic and international disinfectants;
4. The lethal density of OH is about one thousandths of the spray density for other disinfectants—this will be helpful for eliminating microbial contamination efficiently and rapidly in large spaces, e.g. bed-space areas; and
5. The OH mist or fog drops oxidize the bacteria into CO2, H2O and micro-inorganic salts. The remaining OH will also decompose into H2O and O2, thus this method will eliminate microbial contamination without pollution. 1 Bai et al, “Experimental studies on elimination of microbial contamination by hydroxyl radicals produced by strong ionisation discharge”, Plasma Science and Technology, vol. 10, no. 4, August 2008